1. Field of the Invention
The present invention relates to an electric power generation control apparatus capable of controlling an electric power generation of a vehicle alternator mounted on a vehicle such as a passenger car and a truck.
2. Description of the Related Art
In the recent years, there has increased a tendency to effectively use the amount of electric power generation of a vehicle alternator mounted on a vehicle and rotationally driven by an internal combustion engine mounted on the vehicle. In order to achieve such a demand, there are conventional well-known techniques comprising an electric power generation control apparatus for effectively using the electric power generated by the vehicle alternator. The electric power generation control apparatus controls the regeneration to supply an exciting current for a rotor of the vehicle alternator to a battery by using a transistor chopper exciting circuit. For example, Japanese laid open publication No. S62-203599 has shown one of those conventional techniques.
In the electric power generation control apparatus, a field winding is connected to a bridge circuit that comprises a pair of arms made of power transistors and a pair of arms made of diodes. The ON and OFF control of the power transistors allows to flow the exciting current through the field winding from a battery through the bridge circuit, and also allows the regeneration of the exciting current flowing through the field winding to the battery through the bridge circuit.
The technique disclosed in the Japanese patent laid open publication No. 62-203599 is capable of performing the regeneration of electric power in spite of the state of the generation of the electric power in a vehicle alternator. This technique involves a drawback in which sparks thereby arise at the electric power terminals of the battery because the battery cannot receive the regenerated electric power under the state of electric load of a relatively low, of a high capability of the electric power generation (a high speed revolution of an internal combustion engine), and of a fully charged battery.
On the contrary, no sparks occurs at the electric power terminals of the battery if the electric power generation control apparatus disclosed in the conventional technique, for example as disclosed above, is not used. However, this requires a long time period until the adequate reduction of a fly wheeling current when the circulation current flows through a fly wheeling diode, and it further takes a long time period until the adequate reduction of torque of the vehicle alternator when an electric load enters ON and the like. As a result, this case causes a problem that the number of revolution of the engine is reduced. In particular, during the idling of the engine, a large reduction of the number of revolution of the engine has a high possibility to cause an engine stall. In order to avoid the engine stall, it is necessary to increase the number of revolution of the engine during the idling. However, this requirement is contrary to the recent demand of enhancement of fuel economy and of reduction of noise.